Though the stratigraphical and palaeogeographical framework of the Quaternary in Poland is still to be completed, several crucial points have been confirmed recently. The preglacial series, accepted for years as belonging to the Lower Pleistocene, is undoubtedly of Early Pliocene age, with a huge hiatus above almost until the uppermost Lower Pleistocene. The earliest glaciation in Poland (Nidanian) occurred at about 900 ka BP when the ice sheet reached the mid-southern part of the country. The following Podlasian Interglacial embraced the Brunhes/Matuyama boundary in the middle, in a similar fashion to the corresponding Cromerian Complex in Western Europe. The late Early and early Middle Pleistocene interglacials in Poland comprised 2–3 optima each, whereas every one of the younger interglacials was characterised by a single optimum only. The Late Vistulian ice sheet was most extensive in the western part of Poland (Leszno Phase) whereas the younger Poznań Phase was more extensive in the central and eastern part of the country. This was due to the varied distance from the glaciation center in Scandinavia, making the ice sheet margin reach a terminal position in different times. Palaeoclimatological research in the Tatra Mountains has provided new evidence for the atmospheric circulation over Europe. During cold phases of the Pleistocene in Poland a continental climate extended further westwards, quite the opposite that occurring during warmer intervals.
The surface textures of almost 1300 quartz grains in the 0.8-1.0 mm and 0.5-0.8 mm size fractions were studied in order to analyse the effects of frost weathering. Some grains had undergone periglacial processes in present-day active layers in Canada, Spitsbergen and Mongolia, whereas other grains were sampled from a former active layer in Poland. Microstructures were studied under a scanning electron microscope and the results statistically analysed in order to distinguish characteristic microstructures resulting from frost weathering. The quartz grains with these microstructures had been deposited by fluvial, aeolian and glacial processes and their characteristic microstructures are classified as primary microstructures. Microstructures that developed on primary ones as a result of frost weathering are called secondary microstructures. The most characteristic secondary frost weathering microstructures on the quartz grains are (1) small breakage blocks (<10 μm), (2) big breakage blocks (>10 μm) and (3) single small conchoidal fractures (<10 μm). These secondary microstructures developed commonly on the following primary microstructures: (1) sharp edges of big conchoidal fractures (>10 μm), (2) microsteps, (3) edge roundings and (4) crescentic gouges. These findings facilitate the reconstruction of cryogenic conditions, support the recognition of ancient active layers and indicate grains that are particularly susceptible to frost weathering.
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